Discussion

Cardiac tumours in paediatrics are rare, with an estimated incidence of 0.027% to 0.3%. ^{Reference Bassi, Azzarelli, Vaccaro and Mazzatenta1} The majority are benign, with rhabdomyomas being the most common, followed by fibromas, myxomas, and haemangiomas, ^{Reference Drolet, Frommelt and Chamlin2} the latter accounting for less than one-twentieth of all primary cardiac tumours. Clinical presentation varies based on tumour location and size, with manifestations including cardiac murmurs, heart failure, arrhythmias, and syncope. ^{Reference Morin, Griffin and Beroukhim3,Reference Burke, Johns and Virmani4} In some cases, blood flow obstruction or pericardial involvement may lead to severe complications such as embolism or cardiac tamponade. In neonates and children, intracardiac haemangiomas are associated with high mortality, primarily due to high-output heart failure secondary to arteriovenous shunting through the tumour, massive haemorrhage from vascular fragility, or central nervous system involvement. ^{Reference Bassi, Azzarelli, Vaccaro and Mazzatenta1}

Diagnosis relies on non-invasive imaging techniques. Echocardiography is the first-line modality, allowing for mass characterisation and haemodynamic assessment with high diagnostic sensitivity. ^{Reference Morin, Griffin and Beroukhim3} In this case, transthoracic echocardiography identified a hyperechoic, vascularised lesion in the interventricular septum with a peak right ventricular outflow tract gradient of 112 mmHg. Cardiac magnetic resonance imaging confirmed a highly vascularised mass with an extracellular volume of 67%, strongly suggesting a haemangioma.

Echocardiographic assessment is essential for the detection and preliminary characterisation of cardiac tumours in paediatrics. Although tissue diagnosis is not usually evident in the initial evaluation, analysing the morphology, echogenicity, homogeneity, size, and location of the mass helps guide diagnostic suspicion. ^{Reference Morka, Kohut and Radzymińska-Chruściel5,Reference Meng, Lai, Lima, Tong, Qian and Lai6} Additionally, echocardiography facilitates the identification of associated haemodynamic alterations, such as outflow tract obstruction, valvular insufficiency, or ventricular dysfunction. The use of 2D and 3D imaging from multiple views allows for evaluating the tumour’s interaction with cardiac structures and the potential presence of pericardial or pleural effusions. Colour Doppler interrogation with a low Nyquist threshold is useful for assessing tumour vascularisation, which in this case suggested a probable haemangioma.

Among the previously discussed haemodynamic alterations, right ventricular outflow tract obstruction is rare and typically presents clinically with signs of right heart failure. ^{Reference Arjomand, Van Decker, Fyfe, Nixon, Wolf and Sokil7} Our patient experienced functional class deterioration without additional associated symptoms. From an echocardiographic perspective, no right atrial dilation or right ventricular dysfunction was observed, both of which are important parameters for follow-up assessment.

Due to these findings, cardiac magnetic resonance imaging was performed for better tissue characterisation. Magnetic resonance imaging is the gold standard for cardiac tumour tissue characterisation. ^{Reference Fogel, Anwar and Broberg8,Reference Inserra, Cannizzaro and Passaniti9} The acquired sequences allow for evaluating different aspects of both intracellular and extracellular tissue composition. The calculation of extracellular volume, recently incorporated into imaging protocols, has improved diagnostic guidance ^{Reference Medina Perez, Lichtenberger and Huppmann10} and was a key factor in this case. Additionally, the contrast-enhanced imaging findings were consistent with high vascularisation, later confirmed by cardiac catheterisation.

Given the rarity of this case and the lesion’s location, coronary CT angiography was performed, identifying vascular supply from a septal branch of the left anterior descending artery. This information was crucial for therapeutic planning, ruling out surgical intervention due to difficult access and the risk of complications. Instead, an interventional approach with cardiac catheterisation and embolisation of the septal branch using an Interlock Coil device was chosen. Post-procedure angiography confirmed complete occlusion without immediate complications. While histopathological confirmation is necessary for a definitive haemangioma diagnosis, endomyocardial biopsy was not considered due to the high risk of embolism and haemorrhage.

This case highlights the importance of echocardiography in detecting cardiac tumours and the need to integrate multiple imaging modalities for lesion characterisation and therapeutic planning. Furthermore, it underscores the role of cardiac catheterisation as a less invasive alternative for managing tumours with significant haemodynamic obstruction, optimising prognosis and reducing risks associated with open-heart surgery. Combining these strategies facilitates an individualised approach to managing rare paediatric cardiac tumours.